Simultaneous T1, T2, R2*, PDFF, and triglyceride quantification in the head and neck using magnetic resonance fingerprinting on a 1.5T MR-Linac.
McCullum L, Subashi E, Mulder SL, Taylor BA, Hwang KP, Fuller CD (+1 more)
Abstract
BackgroundThe extraction of quantitative biomarkers on the MR-Linac, which have been shown to be promising in the head and neck, remains a significant challenge due to the strict time constraints.PurposeThe purpose of this study was to assess the technical feasibility of magnetic resonance fingerprinting (MRF) to simultaneously extract quantitative T1, T2, R2*, PDFF, and triglyceride composition in the head and neck on the MR-Linac.MethodsInversion-prepared, multi-echo, golden angle radial, variable flip angle, MRF data were acquired on a 1.5T MR-Linac. The data were corrected for phase errors in the bipolar multi-echo acquisition followed by low rank reconstruction with total variation regularization. A dictionary of signals parameterized by T1/T2 was calculated with an extended phase graph algorithm. The singular images were constructed using a signal subspace from the dictionary and the first singular images were then jointly fit for R2* and PDFF using the off-resonance information from an independent B0 map. The complete set of B0/T2*-corrected fat-water separated water singular images were fitted for T1/T2. Triglyceride composition was computed using the multi-echo complex readout. Three phantoms and three healthy volunteers were assessed for accuracy, repeatability, and reproducibility against validated reference sequences across five days using a test-retest setup.ResultsAll coefficients of determination were at least 0.9 against reference sequences in standard phantoms across all quantitative parameters. The repeatability and reproducibility averaged under 5% in phantoms and under 10% in healthy volunteers.ConclusionThe proposed MRF acquisition demonstrated the potential to replace the current time-intensive sequences on the 1.5T MR-Linac, thus increasing the adoption of specialized quantitative imaging biomarker approaches at high temporal density in the head and neck.